A radiation tube (radiation generating tube) accelerates electrons emitted from an electron source to high energy and irradiates a target with the accelerated electrons to generate radiation such as X-rays. The radiation generated at this time is emitted in all directions. In light of this, a container holding the radiation tube or the circumference of the radiation tube is covered with a shield member (radiation shielding member) such as lead so as to prevent unnecessary radiation from leaking outside. Thus, it has been difficult to reduce the size and weight of such a radiation tube and a radiation generating apparatus holding the radiation tube.
Japanese Patent Application Laid-Open No. 2007-265981 discloses a transmission type multi X-ray generating apparatus for shielding unnecessarily emitted X-rays by arranging shields each on an X-ray emission side and an electron incident side of the target.
It has been difficult for such a target (anode)-fixed type transmission type radiation tube to generate high-energy radiation because the target has a relatively low heat radiation. The X-ray generating apparatus disclosed in Japanese Patent Application Laid-Open No. 2007-265981 is configured such that the target is bonded to the shield member, which allows heat generated in the target to be transferred to and dissipated through the shield member, thereby suppressing an increase in temperature of the target.